The purpose of our original research (1969-71) was to collect, organize and analyze the data from private and Federal manuscript censuses in order to study the comparative rates of social mobility for the Negro, Irish and German populations of Philadelphia, 1850-1880. The research focused on the question of whether the disabilities and burdens faced by the Negro were peculiar to his historical experience, or whether they were simply obstacles which every immigrant group entering American society has had to overcome. The purpose of our expanded research (1971-73) was to study three topics each valuable in its own right, but selected primarily because each provided a new and valuable perspective from which comparative social mobility could be studied: family structure, social stratification, and neighborhood. In each of these instances, the comparative perspective was broadened to include native-white-Americans. During this period, too, we collected additional data from the Federal manufacturing manuscript censuses describing the process of industrialization, from city business directories describing business growth, and from other sources describing the development of transportation, all of which were altering the social structure upon which the measurement of social mobility depends. The purpose of our proposed renewal of research (1973-76) is to provide the additional time and support required to undertake a through analysis of this unprecedentedly large, rich and inter-dependent body of data so that the relationships between socioeconomic change and ethnicity can be understood as manifested in social mobility, industrialization, neighborhood, family structure and social structure.